antigen

noun antigen

• dander — small particles or scales of hair or feathers
• irritant — tending to cause irritation; irritating.
• pollen — the fertilizing element of flowering plants, consisting of fine, powdery, yellowish grains or spores, sometimes in masses.
• ragweed — any of the composite plants of the genus Ambrosia, the airborne pollen of which is the most prevalent cause of autumnal hay fever, as the common North American species, A. trifida (great ragweed or giant ragweed) and A. artemisiifolia.
• dust mite — any of various mites, especially Dermatophagoides pteronyssinus and D. farinae, that ingest shed skin cells and may cause allergic reactions.